For more information about input focus, see Chapter 13, "Visual Design."
Keyboard selection relies on the input focus to define selected objects. The input focus can be an insertion point, a dotted outline box, or some other cursor or visual indication of the location where the user is directing keyboard input.
Note
For more information about input focus, see Chapter 13, "Visual Design."
In some contexts, selection may be implicit with navigation. When the user presses a navigation key, you move the input focus to the location (as defined by the key) and automatically select the object at that location.
In other contexts, it may be more appropriate to move the input focus and require the user to make an explicit selection with the Select key. The recommended keyboard Select key is the SPACEBAR, unless this assignment directly conflicts with the specific context — in which case, you can use CTRL+SPACEBAR. (If this conflicts with your software, define another key that best fits the context.) In some contexts, pressing the Select key may also unselect objects; in other words, it will toggle the selection state of an object.
In text contexts, the user moves the insertion point to the desired location using the navigation keys. Set the anchor point at this location. When the user presses the SHIFT key with any navigation key (or navigation key combinations, such as CTRL+END), set that location as the active end of the selection and select all characters between the anchor point and the active end. (Do not move the anchor point.) If the user presses a subsequent navigation key, cancel the selection and move the insertion point to the appropriate location defined by the key. If the user presses LEFT ARROW or RIGHT ARROW keys, move the insertion point to the end of the former selection range. If UP ARROW or DOWN ARROW are used, move the insertion point to the previous or following line at the same relative location.
You can use this technique in other contexts, such as lists, where objects are logically contiguous. However, in such situations, the selection state of the objects logically included from the anchor point to the active end depend on the selection state of the object at, or first traversed from, the anchor point. For example, if the object at the anchor point is selected, then select all the objects in the range regardless of their current state. If the object at the anchor point is not selected, unselect all the items in the range.
You use the Select key for supporting disjoint selections. The user uses navigation keys or navigation keys modified by the SHIFT key to establish the initial selection. The user can then use navigation keys to move to a new location and subsequently use the Select key to create an additional selection.
In some situations, you may prefer to optimize for selection of a single object or single range. In such cases, when the user presses a navigation key, reset the selection to the location defined by the navigation key. Creating a disjoint selection requires supporting the Add mode key (SHIFT+F8). In this mode, you move the insertion point when the user presses navigation keys without affecting the existing selections or the anchor point. When the user presses the Select key, toggle the selection state at the new location and reset the anchor point to that object. At any point, the user can use the SHIFT+navigation key combination to adjust the selection from the current anchor point.
When the user presses the Add mode key a second time, you toggle out of the mode, preserving the selections the user created in Add mode. But now, if the user makes any new selections within that selection scope, you return to the single selection optimization — canceling any existing selections — and reset the selection to be only the new selection.